Liquid crystal displays (LCDs) are commonly used as display devices for compact electronic apparatuses. This is not only because they provide good quality images with little power consumption, but also because they are very thin. Generally, a liquid crystal display includes a liquid crystal panel, a backlight module, and a plastic frame receiving the liquid crystal panel and the backlight module. The plastic frame is made of black material and has a high light absorption characteristic. Therefore a rate of utilization of light beams by the backlight module is limited. Various means have been developed to solve this problem.
Referring to FIG. 3 and FIG. 4, a typical liquid crystal display 30 includes a liquid crystal panel 33, a backlight module 35, and a plastic frame 37. The plastic frame 37 includes four side walls 371 perpendicularly connected end to end, and a frame-shaped ledge 373 extending from inner surfaces of the side walls 371. The side walls 371 and the ledge 373 cooperatively form an upper accommodating space and a lower accommodating space. The liquid crystal panel 33 is received in the upper accommodating space, and the backlight module 35 is received in the lower accommodating space.
The backlight module 35 includes a light guide plate 351, a light source 353, and a reflection film 355. The light guide plate 351 includes a light incident surface 3511, a top light emitting surface 3512 perpendicularly adjoining the light incident surface 3511, a bottom surface 3513 perpendicularly adjoining the light incident surface 3511, and three side surfaces 3514 perpendicularly adjoining both the light emitting surface 3512 and the bottom surface 3513. The reflection film 355 is approximately U-shaped. The reflection film 355 encloses the light incident surface 3511, the bottom surface 3513, and one of the side surfaces 3514 farthest from the light incident surface 3511. The light source 353 is located between the light incident surface 3511 and the reflection film 355.
Light beams emitted from the light source 353 enter the light guide plate 351 through the light incident surface 3511. Most of the light beams travel in the light guide plate 351 and become substantially uniform, and then emit from the light guide plate 351 through the light emitting surface 3512. Some of the light beams emit from the bottom surface 3513 and the side surfaces 3514 of the light guide plate 351. Many or most of these light beams are reflected by the reflection film 355 back into the light guide plate 351, and subsequently emit from the light emitting surface 3512. However, one drawback of the backlight module 35 is that the reflection film 355 needs to have a large enough area so as to cover all of the bottom surface 3513 and said farthest side surface 3514 of the light guide plate 351, as well as the light source 353. Therefore the cost of the reflection film 355 is high. Further, the reflection film 355 is fixed by adhesive tape, which can make the process of manufacturing the backlight module 35 complicated and difficult.
Referring to FIG. 5, another typical liquid crystal display 50 is shown. The liquid crystal display 50 has a high rate of utilization of light beams, and includes a liquid crystal panel 53, a backlight module 55, a plastic frame 57, and a frame-shaped absorbing strip 59. The plastic frame 57 includes four side walls 571 perpendicularly connected end to end, and a ledge 573 extending from inner surfaces of the side walls 571. The side walls 571 and the ledge 573 cooperatively form an upper accommodating space and a lower accommodating space. The liquid crystal panel 53 is received in the upper accommodating space, and the backlight module 55 is received in the lower accommodating space. The absorbing strip 59 is provided on a peripheral part of the liquid crystal panel 53 and a part of the plastic frame 57 surrounding the liquid crystal panel 53. The absorbing strip 59 can for example be a frame-shape piece of light blocking tape. The plastic frame 57 is made from white resin material, by an injecting-mold method. The plastic frame 57 has a high light reflection ratio.
The backlight module 55 includes a light guide plate 551, a light source 553, and a reflection film 555. The light guide plate 551 includes a light incident surface 5511, a top light emitting surface 5512 perpendicularly adjoining the light incident surface 5511, a bottom surface 5513 perpendicularly adjoining the light incident surface 5511, and three side surfaces (not labeled) perpendicularly adjoining the light emitting surface 5512 and the bottom surface 5513. The light source 553 is located adjacent to the light incident surface 5511 of the light guide plate 551. The reflection film 555 is located below the bottom surface 5513 of the light guide plate 551.
In operation of the liquid crystal display 50, light beams leaking from, the side surfaces of the light guide plate 551 reach inner surfaces of the plastic frame 57, and are reflected by the plastic frame 57. Therefore a rate of utilization of light beams of the liquid crystal display 50 is high. Furthermore, the absorbing strip 59 absorbs light beams reaching edges of the liquid crystal panel 53, thereby facilitating uniformity of light emission of the liquid crystal display 50. However, the absorbing strip 59 increases the cost of the liquid crystal display 50, and makes a process of manufacturing the liquid crystal display 50 somewhat complicated and difficult.
What is needed, therefore, is a liquid crystal display that can overcome the above-described deficiencies.